By suggesting that female animals hide their sexual qualities because unwanted male attention may be detrimental to their fitness, the new research, published in Animal Behaviour, comes up with an original explanation to solve this mystery of animal biology.

Up to now, scientists had come up with two hypothesis as to why females didn't display more decorative features to avoid this rejection by male counterparts. The first one was that because females are the ones bearing the descendants or laying the eggs, they have a greater need for camouflage from predators.

Second, scientists found that ornamentation could affect fecundity. In this latest study the authors indeed explain that the "fitness cost of producing the ornamented trait would be high and females would do better to spend their limited resources on additional eggs".

The cost of harassment

Reviewing these different hypothesis, they realised that unattractive physical traits could also be interpreted as a protection against too much male attention.

"We suggest that if female ornaments signalled their sexual quality, females could suffer increased sexual harassment by males and this could be especially costly to fitness", says co-author David Hosken. Repeated sexual advances and harassment would lead to females losing energy and physical well-being.

Although this is still just another hypothesis, the scientists believe it is an interesting lead to follow-up on in future research. "We are not suggesting that male harassment of attractive females is the only explanation for lack of sexual ornamentation in females but want to alert researchers to the idea that this could be a contributing factor," comments Hosken.